A woman who accused her former partner of sexually abusing their daughter behaved in a "calculated" fashion after deliberate planning , a High Court judge has concluded .

Mrs Justice Russell said the woman's plan was to sever the relationship between the girl - now 10 - and her father.

The judge said she had not found any of 12 allegations against the man proved on the balance of probabilities.

Mrs Justice Russell said police and social service bosses had already investigated and concluded that there was "no basis for taking the matter further".

The judge said the man had asked for a finding that his former partner fabricated the allegations to "undermine contact" and caused the girl serious emotional harm.

She ruled in his favour following a hearing in the Family Division of the High Court in London.

No one involved was identified in a written judgment.

"(The man) denied all the allegations," said Mrs Justice Russell. "I do not find any of the allegations of sexual abuse are proved on the balance of probabilities."

The judge added: "Her delay in reporting allegations to the local authority does not ring true and (is) not indicative of a parent who believes that their child has been abused."

Mrs Justice Russell said allegations surfaced in January 2009 but the man had weekend contact with the girl "without any difficulties arising" between March and July of 2009.

"Either she did not believe that sexual abuse had ever taken place, or she cynically and deliberately placed her daughter at risk of further abuse," said the judge.

"On balance, I find it more likely than not that she did not believe her daughter to be at risk. I do not think that she would place (the girl) in danger, but rather that she knew she was safe because the allegations had no foundation and were not true."

She added: "Such calculated behaviour can only be as a result of deliberate planning. The plan was to sever the relationship between (the girl) and her father."